Influence of silica fume on mechanical and durability of pervious concrete

Abstract

Anecdotal evidence has suggested that silica fume is beneficial for improving pervious concrete strength and durability. To determine how silica fume influences a variety of pervious concrete properties and durability the research presented herein studied the performance of paste and ultimately two types of pervious concrete. Since paste properties control pervious concrete workability, compaction, and ultimately performance, rheological properties of a series of paste mixtures with proportions and admixture dosages representative of field-placed pervious concrete were used to provide baseline behavior. Paste samples were continuously mixed and tested over time with the amount of silica fume replacing Portland cement up to 10%. The impact of silica fume on pervious concrete was first investigated on samples produced with a fixed compaction energy, as common in the field, using smooth river gravel aggregate. For pervious concrete produced with fixed compaction energy, changes in workability were reflected in void content which significantly impacted performance. Since void content and density changes significantly impacted performance, lastly samples were produced at a fixed void content using both smooth river gravel but also rougher limestone coarse aggregate. In fixed void content pervious concrete the compaction energy was varied to achieve a fixed void content of 20% for all samples. Results show around 5% silica fume produced the best performance of increased workability, strength and durability.